Trimmer construction for variable condensers



March 3, 1959 Y J. WRIGHT 2,876,403

TRIMMER CONSTRUCTIQN FOR VARIABLE CONDENSERS Filed May 15, 1954 INVENTOR. JOHN R. WRIGHT BY v awi-dmag ATTORNEYS TRIMMER CONSTRUCTION FOR VARIABLE CONDENSERS John R. Wright, Watseka, Ill., assignor to Radio Condenser Company, Camden,N.J., ncorporation of New This invention relates ,to a trimmer construction for variable condensers and has particular reference to the provision of trimmers for variable condensers of compact construction such as are used in transistor circuits, the trimmer features adding a minimum of additional dimensions to the variable condenser.

The general objects of the present invention relate to the Provision of trimmer constructions of the type indicated above which are extremely compact and which may be very readily assembled with thelnormahvariable condenser elements. In particular, inaccordance ,with theinvention, the trimmer-formingelements are directly associated with the soldering lugs such as are normally provided on a variable condenser.

These and other objects of the invention particularly relating to details of construction will become apparent from the following description, read in conjunction with the accompanying drawing, in which:

Figure 1 is an end elevation of a variable condenser having trimmers associated therewith;

Figure 2 is a bottom plan view of somewhat over onehalf the condenser illustrated in Figure 1;

Figure 3 is an exploded view showing in perspective the various elements which, in particular, form a trimmer; and

Figure 4 is a perspective view illustrating the mode of assembly of two of the parts involved in providing the trimmer.

Referring first to Figures 1 and 2, there is illustrated therein a two-section condenser which, to a considerable extent, is conventional. This condenser comprises a U-shaped frame 2 of relatively rigid metal in which there is mounted the shaft 4 carrying the variable plates of the condenser sections. This shaft is mounted in a ball bearing indicated at 6 and has its inner end provided with a socket in which a ball 8 is located by a screw 10 threaded in the frame and also provided with a socket. A leaf spring 12 provides a thrust on the shaft 4 toward'the right, as viewed in Figures 1 and 2, and furnishes a predetermined friction serving to hold the movable condenser plates in adjusted position. The movable plates of the respective sections are indicated at 14 and 14' and are secured, as usual, in annular grooves in the shaft 4. To provide rigidity, these plates are secured at one end thereof in an insulating strip 15. The metal parts so far described are, as usual, electrically connected to the frame.

The fixed plates of the two sections are respectively shown at 16 and 16. These are mounted, respectively, in plates 18 by which their spacings are maintained and they are electrically interconnected in their respective groups. The plates 18 are provided with lips 19 which provide for soldering.

Secured in slots in the ends of the frame are insulating plates 20, these being secured at edge portions 22 by inwardly burred edges of the frame slots indicated at 24. Definite positioning of these plates is secured by abutment of shoulders 26 with the frame. Each insulating nited States Patent 0 F 2,876,403 P te e Me 3 95 plateis .provided with a rectangular slot 28 associated with which are edge indentations 30 to provide a pair of bars 32. Soldering lug members are indicated generally at 34 and comprise body portions 36 carrying soldering lugs 40 through the medium of narrow bent connector necks 42. The soldering lugs 40 are provided as usual'with wire-receiving .op enings' 4 4. The body portion of each member is provided .with prongs 38 which are arranged to embrace bars 321and besecnred thereto by ends turned againstthese bars. To the upper edge 48 of each member 34 there is soldered, as indicatedat 46, the lipof a corresponding plate .18. l f I To the extent-so far described the construction may berega rded as conventional, there being associatedwith each set of fixed condenser plates a pair of members'fi i serving for [support "and providing a pair of soldering g 40. t,

In accordance with the present invention, the soldering lug assemblies Iwhichhave. been described serve for .the support of trimmer condenser plate membersias will now be described. For this additional function the body portion-36 of each member 34 is provided with an outwardly extending punched jtab 49-adjacent to its edge 48 A trimmer plate member is indicated generally at .50 and comprises a securing p ortion 52 provided with aslot 54 andan in'd'ntati'on56. Extendingfrom this'sccuririg portion is a loop 58 the outer end of which carries a flat 60 of square or rectangular form having turned corners as indicated at 62 and provided with an enlarged central opening 64. The members 50 are desirably formed of spring brass.

Reference may now be made particularly to Figure 4. A soldering lug member is illustrated therein, and in full lines this member is shown associated with the trimmer element 50. In construction lines there is shown the position of the trimmer element as it is located with respect to the soldering lug member in beginning its association therewith. The slot 54 is of a width sufficient to slip over the soldering lug 40 and also to embrace the neck 42 when the parts are assembled in the full line positions illustrated in Figure 4. The length of the slot 54 is sufficient to enable it to be moved over the soldering lug 40. In assembly it is moved toward the soldering lug from the construction line position illustrated in Figure 4 and is then turned through 90 with movement to engage its notch 56 with the lug or ear 49 against which it is pressed. Soldering then serves to secure the two parts together in the full line position illustrated in Figure 4, the clearance between the shoulders of the soldering lug 40 where it joins the neck 42 and the body portion 36 being just slightly greater than the thickness of the trimmer element material to provide mechanical strength in connection with the engagement of the notch 56 and ear 49, thus providing a firm assembly even before soldering.

As indicated in Figure 2, at each end of the condenser there is a trimmer for one of the condenser sections, it being understood that for a two-section condenser the other end, which is not shown in Figure 2, is symmetrically disposed. At each end, therefore, the condenser frame is provided with a tapped hole for the reception of a screw 66 which passes through an insulating washer 68 having a central hole 70 which is substantially smaller in diameter than the opening 64 in the trimmer member. Interposed between the portion 60 of the trimmer member and the condenser frame is an insulating plate 72 to provide a dielectric for the trimmer condenser, which plate is provided with an opening 74 for the passage of the screw 66. The insulating washer 68 is centered with respect to the opening 64 by means of the ears provided by the turned corners 62. Initially, the members 50 are so formed that the portions 60 will be substantially spaced outwardly from the condenser frame. Adjustment of the screw 66 then serves to force the portions 60 inwardly toward the interposed insulating plate 72 and the frame of the condenser. There is thus secured the required capacity value to provide the trimming action. It may be noted that the insulating plate 72 is held against rotation by reason of its centering by screw 66 and its abutment with the inner projecting lower edge of the supporting insulating plate 20.

From the above description, it will be evident that there is provided a trimmer for each section of a multiple section variable condenser or for the single section of a single section condenser which is readily associated with the conventional elements of the condenser assembly and which provides a negligible projection of any added parts, thereby maintaining the advantage of small size of the variable condenser. In fact, on the bottom of the condenser as illustrated in Figure 1 it will be noted that the sole additional projection occurs where the portion 58 of the trimmer member passes over the edge of the insulating support 20 and by reason of the slight projection of the head of the screw 66.

It will be evident that various changes in detail may be made without departing from the invention as defined in the following claim.

What is claimed is:

A variable condenser and trimmer therefor comprising a metal frame, a shaft mounted in said frame and carrying at least one movable plate, at least one fixed condenser plate, insulating means mounting said fixed plate,

a connector conductiv'ely secured to said fixed plate and provided with an outwardly extending soldering lug and an ear, said soldering lug having a neck and shoulders adjacent to the neck, a conductive trimmer element slotted to embrace the neck of said soldering lug beneath said shoulders and restrained against outward movement thereby, said trimmer element being provided with a notch engaging said ear and being secured to said con nector and comprising a plate member carried by a flexible portion thereof, said plate member being disposed approximately parallel to a portion of said frame and approximately at right angles with respect to the part of the trimmer element embracing the neck of the soldering lug and engaging the ear, and said plate member being provided with ears forming a socket therein, an insulating washer located in said socket, and a screw threaded into said frame through said washer and said plate memher, and being spaced from the latter by said washer, to provide for adjustment of the spacing between said plate member and the frame.

References Cited in the file of this patent UNITED STATES PATENTS 1,712,011 Squire May 7, 1929 1,951,661 Koepping Mar. 20, 1934 1,951,925 Cohen Mar. 20, 1934 2,063,986 Cohen Dec. 15, 1936 2,087,902 Cramer July 27, 1937 2,155,201 Nelson Apr. 18, 1939 

